The present invention relates to a method of forming a cast metal article using a core assembly having a base core with a core element disposed in an opening formed in the base core.
Ceramic cores have previously been utilized to form openings or passages in cast metal articles, such as turbine engine components. The turbine engine components may be blades or vanes. In U.S. Pat. No. 6,929,054, it is suggested that a refractory metal article, such as a wire or sheet, can be cut and utilized as a core element in association with a ceramic base core.
When a core element is used in combination with a ceramic base core, difficulty may be encountered due to the ceramic base core having a different coefficient of thermal expansion than the core element. For example, the core element may be a refractory metal article having a coefficient of thermal expansion of approximately 7.0×10−6 inches per inch per degree centigrade. The ceramic base core may be formed of silica and have a coefficient of thermal expansion of approximately 0.5×10−6 inches per inch per degree centigrade. The relatively high coefficient of thermal expansion of the core element can result in a cracking of the ceramic base core during firing.